The present invention generally relates to an image forming arrangement and more particularly, to an image forming apparatus, for example, in the form of a copying apparatus for effecting formation of a copied image edited from an original image by partially erasing a latent image on a photosensitive member formed through scanning of said original image.
Electrophotographic copying apparatuses may be broadly divided into the so-called analog type copying apparatus in which a latent image is formed by projecting an original image onto a photosensitive member by a reading optical system, and the digital type copying apparatus in which a latent image is formed by an exposure optical system provided separately from the reading optical system, based on image data through quantization of photo-electric conversion signals as obtained by optically reading the original image.
Since the analog type copying apparatus widely used is arranged to effect reading of the original image and exposure of the photosensitive member by one optical system, the construction thereof may be simplified, and copied images of high resolution can be obtained by an inexpensive mechanism.
Meanwhile, the digital type copying apparatus is capable of readily effecting various image editing functions such as magnification variation, image inversion, color conversion specific to color originals, etc., in addition to the processing for improvement of image qualities by applying treatment to the image data.
Incidentally, in order to meet diverse requirements with respect to the image editing, the analog type copying apparatus has also been provided with various image editing functions up to the present.
Of the image editing functions as described above, one function frequently utilized is that for forming a copied image in which a portion of a designated color is removed with respect to a color original (referred to as a designated color removed image).
The above function is particularly effective, for example, in the case where a copied image only of characters is to be formed with respect to an original on which a predetermined portion of a row of black letters is marked with a red underline, etc.
In order to form a designated color removed image, the conventional copying apparatus includes an image sensor for reading an original image as finely divided into picture elements during scanning of the original, and an eraser for partially erasing a latent image formed on a photosensitive member per each predetermined erasing unit section, and is so arranged that, after erasing the latent image corresponding to a designated color portion within the original image by detecting color of each picture element from the output of the image sensor, toner is caused to adhere to the remaining latent image so as to form the copied image.
For the image sensor as referred to above, there is provided a sensor having a high resolving power similar to that in the reading optical system for the general digital type copying apparatus. Meanwhile, for the eraser, one having a resolving power inferior to that of the image sensor is provided from the aspect of cost reduction.
More specifically, the erasing pitch of the eraser generally employed is larger than the picture element pitch of the image sensor. For example, in a copying apparatus generally used, and employing a CCD sensor as an image sensor and an LED array for an eraser, the erasing pitch is set about 3 to 4 times that of the picture element pitch, with the area of the erasing unit section being approximately 9 to 16 times that of the picture element.
In the conventional copying apparatus as described above, there has been such a problem that before the copying function is actually effected after an operator has designated a color of an image to be removed (referred to as a designated image hereinafter) from the original image, it is impossible to confirm whether or not the image desired by the operator can be obtained. In other words, the operator is unable to ensure whether the coped image is right or wrong until the copying function is completed, and the copy paper sheet formed with the copied image has been discharged, thus not being fully confident of the result of copying work.
By way of example, in the case where it is required to make a red portion of an original image blank, such an inconvenience may occur in the copied image that the red portion and a reddish orange colored portion become blank due to an error in the color detection within the copying apparatus, or that a peripheral portion of the red color is made blank, resulting from a difference between the picture element pitch and the erasing pitch, but the operator can not foresee such a state.
As described above, if a copied image not desired by the operator is formed in some cases according to the state of the original image, the copying function at this time becomes useless, with the toner being consumed in an amount more than necessary.
Particularly, in a color copying apparatus in which the exposure and developing are repeatedly effected, waiting-time for the operator is generally long, and if the resultant copied image is one not actually desired, the amount of toner wastefully consumed becomes several times that of a single color copying apparatus.
Furthermore, in the case where the designated image and an image having the same color as the designated image, but not desired to be removed, are mixedly present in one original image, or in the case where the removal is to be stopped with respect to the portion adjacent to the image not desired to be removed in the designated image, if it is possible to correct the designated image as desired for setting, the range of utilization of the copying apparatus may be enlarged. However, in the conventional copying apparatus, the designated image is specified by the designation of color, and partial correction of the designated image can not be effected thereafter.